The communication channel between a transmitter and a receiver may be time varying and dispersive. The dispersion of the channel may result in multipath propagation of transmitted signal; thus, at a receiving destination, more than one receiver chain may be needed to process the multipath received signals. A receiver chain for signals received at each antenna may be necessary. Therefore, multiple receiver chains may be necessary to exploit the multipath signals received at multiple receive antennas. Use of multiple receiver chains increases the power consumption. A mobile station in a communication system may greatly benefit from receive diversity; however, mobile stations generally have limited battery power supply.
Performance of mobile stations, in at least one aspect, is measured with respect to the length of time operating without recharging the battery power supply. Various schemes have been used and deployed in various communication systems to improve the battery life of a mobile station without limiting its operational functionalities. For example, in a communication system, a mobile station may periodically shut off and wake up in predefined assigned time periods to monitor a quick paging channel (QPCH). If the QPCH indicates possibility of a message for the mobile station, the mobile station directs its resources to monitor an assigned paging channel, a broadcast common channel or a common control channel. The directed channel may carry a detailed message directing the mobile station to process other channels. The QPCH carries indications of a page directed to the mobile station. The transmission of QPCH may be at a predefined power level to reach as many mobile stations in the coverage area of the transmitter. The QPCH, and other similar channels, therefore, may be transmitted without exploiting a power control scheme. The data in the QPCH may be hashed for two groups of mobile stations for receiving paging indications at different times. The mobile stations in the first group wake up during one time period to receive a QPCH and the second group at another time period. As a result, the mobile stations may conserve battery power while maintaining full functionalities.
The QPCH contains a single bit message to direct the mobile stations. If a mobile station detects a “zero”, for example, indicating no message during its assigned time period, the mobile station may go back to sleep until the next assigned time period. If the mobile station detects a “one”, for example, indicating a page, the mobile station assigns its resources to monitor other related channels. Receive diversity is beneficial for decoding the paging indication bit in the QPCH.
To benefit from the receive diversity, the receiver may have to turn on multiple receiver chains to process multiple received signals. As a result, the receiver may consume a substantial amount of battery power with respect to the amount of data that it is attempting to decode in the QPCH. Therefore, use of receive diversity for decoding QPCH may adversely effect the battery life of the mobile station. Without use of the receive diversity, the mobile station may erroneously decode the QPCH data resulting in inefficient use of the battery power resources.
To this end as well as others, there is a need for an effective use of receiver diversity for decoding various channels in a communication system.